1. Field
The present invention relates to digital resampling. More particularly, embodiments of the invention involve a method and apparatus for concurrently resampling multiple digital signal streams representing multiple signal rates through a single filter path.
2. Description of Related Art
Digital resampling involves converting a first series of values representing a digital signal sampled at a first rate to a second series of values representing the same digital signal sampled at a second rate. Resampling to a lower sample rate is referred to as down sampling or decimation. Decimation may be performed by filtering the original signal using a digital filter implemented in either software or hardware. Implementing such filters requires a relatively large amount of circuit resources. Implementing a digital filter in software, for example, requires a computer processor, and implementing a digital filter in hardware requires a series of arithmetic components, such as adders and multipliers.
Multiple channel resampling involves concurrently resampling more than one digital signal, and may require use of two or more different filters. Multiple rate resampling has been addressed using, for example, multiple filter paths and a switch for directing each of various signals to a particular filter path. This approach requires an additional set of resources (filter path) for each resampling filter. For example, each filter path may involve pipe-lining signal samples through a series of multipliers and adders, requiring a separate set of multipliers and adders for each signal stream to be processed. For relatively large filters (such as finite impulse response filters of eight weights or more), such an approach can require the use of a large number of resources, particularly if multiple resampling filters are used.
Accordingly, there is a need for an improved method and apparatus for signal resampling that does not suffer from the limitations of the prior art.